Topic: Should the rear tire be off center? - resolved

[KB02]

After getting the rear wheel on my project bike (1978 CB750k) - new wheel donated by a Suzuki Katana - I thought my measurements were off as the tire doesn't appear to be centered in the rear section after I had spacers made up. By my new measurements, it if off center to the frame by about 9/32". Then I looked at a picture taken by HedNut in his project thread, PROJECT CHAOS, and his rear tire appears to be off center, too.

You can see in the pic that the tire is off to the left a little bit as compared to the frame section above it.

Is this right? Or should I get my spacers re-made to get the tire lined up?

[VonYinzer]

Imagine there was a straight line that ran down thw center of the bike lengthwise. It should cut the bike (wheels included) in half perfectly. All things must line up or a dangerous situation could be in your future...

[tlbranth]

The front and rear wheels must line up. That's the important thing. That said, it does appear that your spacing is incorrect - assuming your lacing is good. I have a K0 shop manual that has some measurements in it. I'll see what I can find.

[GammaFlat]

Imagine there was a straight line that ran down thw center of the bike lengthwise. It should cut the bike (wheels included) in half perfectly. All things must line up or a dangerous situation could be in your future...

And here's where the head nod comes from.  The front wheels are not "dead nuts on".  HondaMan has written about this a few times.  He says the front wheel is off just a tad to accommodate dual disk setups somewhere from K1-ish forward (don't recall exactly what year they started to lace the front wheel wrong).   The bikes didn't actually come with dual disks but due to some race regulations... needed to be capable.  I'm sure the keywords "tank slap" or "head nod" would be good to find his postings.  

[HedNut]

Very interesting...I never noticed the wheel was off center! Good observation.  And very interesting topic of discussion.... hmmmmmmmmm  Why?

[mlinder]

Is the axle on that bike lined up perpendicularly?
Meaning, is it at a right angle to the swingarm? To the frame?
Because it doesn't look like it is.
Which means that the back of the tire will be on one side of the center line, while the front of the tire is on the other side of the center line.
This could give the impression that it is off center, as the back of the tire will be off center, and that is kinda what you look at for lining crap up.
If it is perpendicular to the swingarm, is the swing arm running parallel to the frame? Swingarm could be bent, frame could be bent, etc, all possible causes of this seemingly un-perpendicular appearing back wheel.

[grumpy]

Is the wheel dished properly?

[HedNut]

Good Point Mlinder!.... I did just loosen the adjusters and pull the chain off before that pic...so she could be cocked in the frame!?  I'll have to verify

[Raul CB750K1]

Some time ago, a friend of mine with one bike like mine was afraid that his rear tire was off-center. Visually it was, but the only way we thought of checking alignment was using a laser lever -those used in building and masonry-. A photo tripod, a bike standing up vertical, choose two points in the symmetry axis -like stem nut and frame upper tube, align the laser between those two points and check whether the laser cuts the rear wheel in half or not.

[HedNut]

GENIUS!!....lazer bike alignment service! I like it!

[KB02]

I'll have to double check measurments when I get home from work tonight (late..) I have a lazer alliugnment tool thingy and have used it to check the chain allignment and that appears to be dead on (I used the same set of measurements to get that aligned, which is kind of odd...).

I'm running a Mag wheel, not spokes, so I shouldn't have a spoke issue in my case. I'll have to check it with stock tire back in place, too, just for another reference.

Another thing to point out is that, if you look at HedNut's picture, you will see the tire does appear to be lines up with the center of the engine. You can see the top of the Cam chain adjuster which appears to be just off center of the back bone - off to the same side as the tire.

So, Raul, after looking at that picture, that tire is off center to the left as well. Did you guys reset it, or run it as it is?

I've done enough work on this bike that I want it to handle well.

[KB02]

Okay.

Looks like I'm all set. 



Thanks, Raul for that idea. The Laser leveler on the camera tripod was a great idea. I didn't have the best light for the pictures or the procedure, but it worked out just the way I needed it to. Turns out there is a center line painted on the tire and the laser lines right up with it and lit it up great.


To the best of my ability, looks like I had it lines up with the head nut and back bone tube.

[Raul CB750K1]

Cool!


Regarding your question, my friend took the bike to the dealer -it was under warranty- and got it returned aligned. We weren't told what they did, I suspect the rear wheel was not laced properly. It was obvious by the naked eye, and when returned, everything seemed fine but truth be told, he didn't notice any strange behaviour of the bike when the wheel wasn't aligned.

[eurban]

Came into this one a bit late. KB02 here is an older thread where I pondered similar offset rear wheel issues on my 78 750K.

 http://forums.sohc4.net/index.php?topic=7764.0

If you like, read though it, particularly the last few posts where I figured out that Honda actually did some interesting offsetting of the shock mounts/swing arm assemblies, probably for 630 chain clearancing.  Hope this helps you out. . . . .

[dusterdude]

mine is a tad off too,havent had any issues.

[Raul CB750K1]

I figured out that Honda actually did some interesting offsetting of the shock mounts/swing arm assemblies, probably for 630 chain clearancing.  

In such a case the wheel should be off-center to the right side, not the left...

[Dave-and-his-550]

mine is a tad off too,havent had any issues.

I've noticed my rear tire seems to be off center as well, I intended to approach this 'mistake' as it would appear, a little later in my build. This thread has been helpful, and I'll try the laser line up!